As the use of Oracle Database continues to grow, the demand for skilled Oracle Database professionals is also on the rise.
If you are preparing for an Oracle Database interview, it’s important to be familiar with the most commonly asked questions. This will help you demonstrate your knowledge and expertise in Oracle Database, and increase your chances of securing your dream job. In this blog post, we have compiled a list of the top 10 Oracle Database interview questions.
What is an Oracle database, and how does it work?
An Oracle database is a relational database management system (RDBMS) developed by Oracle Corporation that is designed to store, manage and retrieve large amounts of data efficiently. It works by storing data in tables, with each table consisting of columns and rows. The database is accessed through SQL (Structured Query Language), which is used to create, modify and retrieve data from the database.
The Oracle database also includes various features and tools such as data backup and recovery, security, and performance monitoring, which help to ensure the integrity and reliability of the stored data.
How do you create a tablespace in Oracle, and what is its purpose?
A tablespace is a logical storage unit that is used to group related database objects such as tables and indexes. It provides a way to manage the physical storage of database objects, and to control their allocation and growth.
To create a tablespace in Oracle, you can use the CREATE TABLESPACE statement. This statement specifies the name and location of the tablespace, as well as its size and other properties. For example, the following statement creates a tablespace called “users” with a datafile located in the /u01/app/oracle/oradata directory:
CREATE TABLESPACE users
DATAFILE ‘/u01/app/oracle/oradata/users01.dbf’
SIZE 100M
AUTOEXTEND ON;
This statement creates a tablespace called “users” with a datafile located in the specified directory, with an initial size of 100MB and automatic extension enabled.
What is a database schema in Oracle, and how does it differ from a user account?
A database schema is a named collection of database objects, including tables, views, indexes, sequences, and procedures. A schema is created and owned by a database user account, and it provides a way to organize and manage related database objects.
A database user account is a login account that is used to access the database. It provides authentication and authorization for users to perform operations on the database objects. A user account can own one or more schemas, and can have different levels of access to database objects within those schemas.
The main difference between a database schema and a user account is that a schema is a logical container for database objects, while a user account is a login account that provides access to those objects.
Here’s an example of creating a new database user named “jdoe” with a password of “mypassword” and default tablespace of “users”:
CREATE USER jdoe IDENTIFIED BY mypassword
DEFAULT TABLESPACE users;
How do you perform database backup and recovery in Oracle?
Performing database backup and recovery is a critical task in Oracle, as it helps to ensure the availability and integrity of data in case of system failures, human errors, or disasters. Database backup can be performed using physical backups, logical backups, or incremental backups, while recovery can be done through complete recovery, point-in-time recovery, or media recovery. The specific backup and recovery strategy used will depend on the specific needs and requirements of the application and organization, as well as the available resources and infrastructure. Oracle provides several tools and features to perform backup and recovery, such as Oracle Recovery Manager (RMAN), Oracle Data Pump, and Flashback technology.
What is an Oracle database instance, and how is it different from a database?
A database instance refers to the set of memory structures and processes that are used to manage and access a specific Oracle database. An instance is created and started when the database is opened and shut down when the database is closed. It includes background processes such as the database writer and the listener, as well as memory structures such as the buffer cache and the shared pool.
On the other hand, a database refers to the physical files that store the data, such as datafiles, control files, and redo logs. A database can have multiple instances that can access and manage the same database, providing scalability and high availability.
In summary, an Oracle database instance is the runtime environment that manages a specific Oracle database, while a database refers to the physical files that store the data.
What are the different types of database objects in Oracle, and how do you create and manage them?
There are several types of database objects, including tables, views, indexes, sequences, procedures, and functions.
To create a table, you can use the CREATE TABLE statement, specifying the table name, columns, data types, and constraints.
To create a view, you can use the CREATE VIEW statement, specifying the view name and the SELECT statement that defines the view.
To create an index, you can use the CREATE INDEX statement, specifying the table and columns to be indexed, as well as the type of index to be created.
To create a sequence, you can use the CREATE SEQUENCE statement, specifying the sequence name, starting value, and increment value.
To create a procedure or function, you can use the CREATE PROCEDURE or CREATE FUNCTION statement, specifying the name, input parameters, and code to be executed.
How do you monitor and tune the performance of an Oracle database?
To monitor the performance of an Oracle database, you can use various tools and features, such as Oracle Enterprise Manager, SQL Trace, and Automatic Workload Repository (AWR). These tools can help identify performance issues, such as slow SQL statements, high CPU usage, or memory bottlenecks, and provide recommendations for improving performance.
To tune the performance of an Oracle database, you can make adjustments to various database parameters, such as buffer cache size, shared pool size, and sort area size, as well as modify SQL statements or database schema as needed. You can also use features such as partitioning, indexing, and materialized views to improve performance for specific workloads.
What is the role of the Oracle listener, and how do you configure it?
In Oracle, the listener is a process that listens for incoming client connections to the database. When a client requests a connection, the listener directs the connection to the appropriate database instance.
To configure the Oracle listener, you can use the Listener Control utility (lsnrctl), which provides a command-line interface to manage the listener. You can start or stop the listener, view the status and configuration, and make changes to the listener parameters.
For example, to add a new database service to the listener configuration, you can add the following entry to the listener.ora file:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = sales)
(ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
(SID_NAME = sales)
)
)
What is the difference between a primary key and a unique key in Oracle, and how are they used?
A primary key and a unique key are both used to enforce data integrity and uniqueness, but they have some differences in their characteristics and usage.
A primary key is a column or set of columns that uniquely identifies each row in a table. A primary key constraint enforces the uniqueness and non-nullability of the specified columns, and automatically creates an index on those columns. A table can have only one primary key.
A unique key is a column or set of columns that enforces uniqueness, but does not necessarily prevent null values. A unique key constraint enforces the uniqueness of the specified columns, but allows null values. A table can have multiple unique keys.
How do you create and manage database users and privileges in Oracle?
To create and manage database users and privileges in Oracle, you can use SQL statements such as CREATE USER, ALTER USER, GRANT, and REVOKE.
To create a new user, you can use the CREATE USER statement, specifying the username, password, default tablespace, and profile. You can also specify additional properties, such as quotas, roles, and authentication options.
To grant privileges to a user, you can use the GRANT statement, which allows you to grant specific system or object privileges to the user, such as SELECT, INSERT, UPDATE, or DELETE on tables or views. You can also grant roles, which are collections of privileges, to the user.
In conclusion, Oracle is a powerful and widely used database management system that plays a critical role in many organizations. As such, employers seek experienced and knowledgeable professionals who possess a deep understanding of Oracle and its various components. In this blog post, we have covered some of the most common Oracle database interview questions, ranging from basic concepts such as database schema and user accounts to more advanced topics such as backup and recovery, performance tuning, and security. By preparing for these questions and reviewing your Oracle knowledge, you can demonstrate your expertise and increase your chances of landing a job as an Oracle database professional.